The vertebrate embryonic axis consists of serially repeated lements, the most evident of which are the somites. The proper production of somites during somitogenesis is critical to the formation of the axial skeleton. The process of somitogenesis is regulated in part by a genetic clock. Key genes in the Notch, Wnt, and Fgf pathways exhibit cyclic expression with a period that matches the rate of somite formation. Mutations that perturb the proper oscillation of these genes can result in congenital defects of the axial skeleton, including spondylocostal dysostoses. Thus, understanding the regulatory mechanisms that control segmentation clock function is critical to our understanding of skeletal development. Several groups have examined the transcriptional control of oscillatory gene expression linked to the segmentation clock, but comparatively little is known about the post-transcriptional mechanisms that regulate clock function. The investigator hypothesizes that microRNAs may play important roles in the post-transcriptional control of genes linked to the clock. miRNAs are small conserved RNAs that bind to target transcripts and promote mRNA turnover and/or inhibit mRNA translation. She proposes that the function of these miRNAs may contribute to the delays in the negative feedback regulatory loops that underlie oscillatory RNA expression. She has identified miRNAs that are enriched in a pattern that is consistent with potential functions in the segmentation clock, and find that many of these miRNAs are predicted to target the 3'UTRs of oscillatory genes. Identifying miRNAs that function in the segmentation clock would provide a new paradigm to understand the posttranscriptional regulation of the segmentation clock. To pursue this idea it will be critical to generate further preliminary data connecting these candidate miRNAs to potential functions in the clock. The investigator therefore proposes to examine these miRNAs during somitogenesis by validating the enrichment of these candidate miRNAs, examining their expression patterns throughout embryogenesis, and functionally testing their ability to target and regulate expression of oscillatory genes. The experiments proposed here fall directly in the scope of the R03 program, as they represent a small, self-contained project that will produce critical preliminary data for future research. Further, this research falls directly into the mission of the NICHD, examining the mechanisms by which the spatial and temporal control of gene expression during embryogenesis functions to regulate somitogenesis. It is predicted that the research proposed here will provide critical links between miRNA regulation and segmentation clock function, and will provide a base of preliminary data that will support further research into the actual functions of miRNAs during somitogenesis as well as the segmentation clock in a future R01 application. RELEVANCE: The processes of embryonic development that produce the spine and ribs are controlled by a genetic clock. When this clock is perturbed, the results can be congenital defects. This research examines different mechanisms that control the expression of genes that have been linked to this clock. By understanding how the expression of genes in the clock is controlled, we will be better able to target treatments for defects and diseases that arise from misregulation of the clock.